Organic graded spin on BARC compositions for high NA lithography

ABSTRACT

An antireflective coating that contains at least two polymer components and comprises chromophore moieties and transparent moieties is provided. The antireflective coating is useful for providing a single-layer composite graded antireflective coating formed beneath a photoresist layer.

TECHNICAL FIELD

The present disclosure relates to polymer compositions and their use inphotolithography including deep ultraviolet photolithography andsemiconductor fabrication. More specifically, a spin-castablemulti-component organic antireflective coating (ARC) is disclosedwherein the materials composition is varied throughout the thickness ofthe ARC layer such that the complex refractive index of the graded ARClayer varies from the ARC-substrate interface to the ARC-photoresistinterface. As a result, the radiation intensity that is reflected at theARC-photoresist interface is substantially decreased, while the lightthat penetrates the ARC layer is absorbed, thus minimizing the radiationreflected from the underlying substrate. Photolithographic limitationssuch as substrate reflectivity, swing effect and reflective notching canbe reduced, in particular when ultraviolet radiation penetrates theimaging layer at high angles of incidence.

BACKGROUND ART

The extension of 193 nm optical lithography to numerical aperture (NA)values above 1.0, enabled by immersion optical projection systems,provides a means of achieving increased resolution for a printableminimum feature size, and therefore allows for further scaling ofintegrated circuits (IC) by the semiconductor industry.

Current state-of-the-art techniques in optical projection printing (suchas 193 nm immersion lithography at NA=1.2) can resolve features beyond50 nm half-pitch in photoresists with good linewidth control whenplanar, low reflectivity substrates are used. However, when photoresistsare exposed on reflective substrates in the presence of underlyingsurface topography, critical dimension (CD) control problems areexacerbated under high NA imaging conditions, and lead to thedeterioration of the quality of the printed image.

Reflection of light from the substrate/resist interface producesvariations in the light intensity and scattering in the resist duringexposure, resulting in non-uniform photoresist linewidth upondevelopment. Light can scatter from the interface into regions of theresist where exposure was not intended, resulting in linewidthvariations. The amount of scattering and reflection will typically varyfrom region to region resulting in linewidth non-uniformity.

To eliminate the effects of chromatic aberration in exposure equipmentlenses, monochromatic or quasi-monochromatic light is commonly used inresist projection techniques. Unfortunately, due to resist/substrateinterface reflections, constructive and destructive interference isparticularly significant when monochromatic or quasi-monochromatic lightis used for photoresist exposure. In such cases the reflected lightinterferes with the incident light to form standing waves within theresist. In the case of highly reflective substrate regions, the problemis exacerbated since large amplitude standing waves create thin layersof underexposed resist at the wave minima. If the resist thickness isnon-uniform, the problem becomes more severe, resulting in variablelinewidth control.

More specifically related to high NA optical imaging, photolithographicsystems that utilize high NA lenses cause light to diffract at highangles. This deviation from normal incidence causes increasedreflectance at the resist-air and resist-substrate interfaces, thusexacerbating the problem. Increased reflectance in turn causes anincrease in both standing waves and CD swing.

In addition to the challenges posed by the use of high NA opticalsystems described above, additional difficulties arise in this field dueto the fundamental loss in image contrast that occurs for the transversemagnetic (TM or p-) polarization state at large oblique angles (T.Brunner et al., Proceedings of SPIE Vol. 4691, p.1, 2002). This loss inTM image contrast at high angles adds up to other sources of imagecontrast degradation such as blocking of diffraction orders at the pupiledge, defocus effects, image flare effects, stage vibrations, etc.

Linewidth control problems due to non-uniform reflectance also arisefrom substrate topography. Any image on the wafer will cause impinginglight to scatter or reflect in various uncontrolled directions(reflective notching), affecting the uniformity of resist development.As the topography becomes more complex with efforts to design morecomplex circuits, the effects of reflected light become much morecritical (H. Yoshino et al., Journal of Vacuum Science and Technology B,Vol. 15, p.2601, 1997).

As a result of the optical effects at high NA and reflective notchingdescribed above, extending the resolution capability of 193 nmlithography requires reflectivity control over a wider range of angles.

A common method to address problems related to reflectivity controlwithin imaging layers, is to apply an antireflective coating (ARC). Atop ARC (TARC) deposited over the photoresist layer can significantlyreduce the swing effect by reducing the reflectivity at theair-photoresist interface, however a TARC does not reduce the notchingproblem. Instead, a bottom ARC (BARC) formed beneath the photoresistlayer is capable of eliminating both the swing and notching problems,and has emerged as the most effective reflectivity solution whileinterfering the least with the lithographic process.

Two types of BARC layers are commonly used by the semiconductorindustry. Spin-on BARCs are typically organic materials applied as aliquid formulation to the semiconductor substrate from a spin-coatingstation (track). After the BARC film is formed, a high temperature bake(post-apply bake) is used to remove the casting solvent and to crosslinkthe polymer components, so as to form a BARC layer that is impervious tothe casting solvent used in the photoresist formulation that is coatedsubsequently. In this case, the optical properties are defined by thechemical functionality of the polymer components present in theformulation.

Alternatively, BARCs deposited through radiation assisted techniquessuch as chemical vapor deposition (CVD), high density plasma,sputtering, ion beam or electron beam are typically inorganic or hybridmaterials (e.g. silicon nitrides, silicon oxynitrides, hydrogenatedsilicon carboxynitrides, or combinations thereof) that are applied froma gas phase in a stand-alone deposition chamber, utilizing precursorscapable of being volatilized, combined with gaseous co-reactants andconverted to their corresponding hybrid or inorganic derivatives at hightemperatures or assisted by plasma conditions. In this case, thechemical nature of the precursors and the reactant concentration ratiosdefine the net chemical composition and the optical properties of thedeposited BARC layer.

In any case, as the NA exceeds 1.0, a homogeneous single layer bottomantireflective coating (BARC) may not suffice in keeping substratereflectivity below 1% at all incident angles, as indicated by Abdallahet al. (Proceedings of SPIE, Vol. 5753, p.417, 2005). Instead,strategically structuring BARCs has been reported as the preferredapproach to ameliorate the detrimental side effects of high-NA imagingand reflective notching when practicing high resolution lithography (K.Babich et al., Proceedings of SPIE, Vol. 5039, p.152, 2003). Suchstrategy includes the use of discrete or continuous bottomantireflective multilayers with optical properties defined throughoutthe antireflective element(s) in such a way that the optical constantsat the top of the BARC surface are approximately or identically equal tothose of the photoresist at the exposure wavelength, to minimizereflection at the photoresist-BARC interface. The bottom section of theBARC is highly absorbing at the exposure wavelength, to minimizereflection from the ARC-substrate interface back into the photoresist.This idea has been accomplished by the use of either a multilayer BARCor a continuously graded BARC.

In the case of a multilayer BARC, two or more antireflective layers withdistinct and properly selected refractive index (n) and absorptioncoefficient (k) are consecutively applied on the semiconductorsubstrate, thus forming an antireflective stack with enhanced opticalproperties with respect to a single layer BARC. The simplest case for amultilayer BARC, namely a dual-layer BARC, has been previously describedas being effective at reducing unwanted reflectivity in semiconductorsubstrates, by using combinations of all-organic (Abdallah et al.,Proceedings of SPIE Vol. 5753, p.417, 2005), organic-inorganic(Ghandehari et al., U.S. Pat. No. 6,867,063) or all-inorganic materials(Linliu et al., U.S. Pat. No. 6,479,401).

Continuously graded BARC films with n and k values that can be tuned andvaried throughout the depth of the antireflective layer can be generatedusing plasma-enhanced chemical vapor deposition (PECVD) methods, wherethe reactant feed ratios are continuously changed during the CVD BARCdeposition process. Such is the case for the deposition of gradedsilicon oxycarbide (U.S. Pat. No. 6,297,521), graded silicon oxynitride(U.S. Pat. No. 6,379,014) or graded hydrogenated silicon carboxynitride(U.S. Pat. No. 6,514,667) BARC layers. Alternatively, a chemicallyuniform CVD-deposited BARC layer can be optically graded by chemicallymodifying the top surface with a plasma treatment (Applied Optics, Vol.43, p.2141, 2004).

The advantageous optical properties of structured BARCs such as thosecomposed of a multilayered or graded antireflective film are met at theinevitable expense of added complexity to the lithographic process. Asimple spin-on dual-layer BARC requires the use of two separateformulations and coating steps, which can increase the number of defectsintroduced on the substrate before the photoresist layer is applied, andrepresents a reduction in wafer throughput. Analogously, a graded CVDBARC necessitates a separate deposition chamber, which adds to the costof the manufacturing process, and also represents a throughput reductionwith respect to an all-track processing, due to the need to transportthe wafers from the track to the CVD tool and back (“How AR CoatingsStack Up”, L. Peters; Semiconductor International, September 2005).

SUMMARY

The present disclosure provides an improved process for lithographicimaging, and especially at high NA, and in particular where highlyreflective substrates are utilized, or when embedded topography ispresent in the semiconductor substrate.

The present disclosure comprises the formation and use of a single-layerspin-on graded BARC having strategically designed optical qualities. Theoptical properties qualities make possible the enhancement of thecontrol of design features below 65 nm.

The antireflective coating compositions are characterized by thepresence of two or more polymer components and by having chromophoremoieties and transparent moieties. The polymer components within theantireflective coating composition individually segregate to the top(ARC-photoresist) or bottom (ARC-underlayer) interfaces, thus impartinggraded optical properties to the antireflective layer. The presentdisclosure also encompasses methods of using the graded antireflectivecoating compositions of the disclosure to pattern underlying materiallayers on a substrate. The present disclosure also encompasseslithographic structures such as a patterned combination of resist layerand graded antireflective layer.

In one aspect, the present disclosure encompasses a composition suitablefor formation of a spin-on graded antireflective layer, the compositioncomprising:

-   -   (a) two or more polymers wherein at least one of the polymers        has at least one chromophore moiety and at least one of the        polymers has at least one transparent moiety,    -   (b) a crosslinking component, and    -   (c) an acid generator.

At least two of the polymer components chemically differ from eachother. The polymer components are typically random copolymers selectedfrom the group of homopolymers or copolymers selected from the groupconsisting of polybisphenols, polysulfones, polycarbonates,polyhydroquinones, polyphthalates, polybenzoates, polyphenylethers,polyhydroquinone alkylates, polycarbamates, polymalonates and mixturesthereof. These moieties are typically functionalized in order to tunethe required physical properties of the polymer (optical constants,surface energy). The polymer components also typically contain aplurality of reactive sites distributed along the polymer for reactionwith the crosslinking component. The acid generator is typically athermally activated acid generator.

In another aspect, the present disclosure is directed to a method offorming a patterned material layer on a substrate, the methodcomprising: providing a substrate having a material layer on a surfacethereof; forming a graded antireflective coating layer wherein thegraded antireflective coating comprises a plurality of polymercomponents that chemically differ from each other and wherein saidplurality of polymer components contain at least one moiety being achromophore to preselected imaging radiation wavelength and at least onemoiety transparent to said preselected imaging radiation wavelength,over the material layer, depositing a photoresist composition on thesubstrate to form a photoresist imaging layer on the material;optionally applying a topcoat layer; patternwise exposing the imaginglayer to radiation thereby creating a pattern of radiation-exposedregions in the imaging layer, selectively removing portions of theimaging layer and the antireflective layer to expose portions of thematerial layer, and etching the exposed portions of the material layer,thereby forming the patterned material feature.

The material to be patterned is typically a conductive, semiconductive,magnetic or insulative material, more typically a metal. These and otheraspects of the invention are discussed in further detail below.

Another aspect of the present disclosure relates to a structurecomprising: a single-layer graded antireflective coating wherein thesingle-layer graded antireflective coating comprises a plurality ofpolymer components that chemically differ from each other and whereinthe plurality of polymer components contain at least one moiety being achromophore to preselected imaging radiation wavelength and at least onemoiety transparent to the preselected imaging radiation wavelength,located beneath a photoresist layer;

-   -   the photoresist;    -   there being a second interface between the single-layer        composite graded antireflective coating and substrate;    -   the single-layer composite graded antireflective coating        comprises optical properties providing substantial control of        features sizes below 65 nm; the plurality of polymer components        within the single-layer composite graded antireflective coating        substantially segregate between the first interface and second        interface.

Still other objects and advantages of the present disclosure will becomereadily apparent by those skilled in the art from the following detaileddescription, wherein it is shown and described only in the preferredembodiments, simply by way of illustration of the best mode. As will berealized, the disclosure is capable of other and different embodiments,and its several details are capable of modifications in various obviousrespects, without departing from the disclosure. Accordingly, thedescription is to be regarded as illustrative in nature and not asrestrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure may be better understood, and its numerousobjects, features, and advantages made apparent to those skilled in theart by referencing the accompanying drawings.

FIG. 1 shows structures that are suitable monomer units of polymercomponents for graded antireflective coating compositions of thedisclosure.

FIG. 2 shows examples of structures of polymer components for gradedantireflective coating compositions of the disclosure.

FIG. 3 shows values of the refractive index (n) and extinctioncoefficient (k) at 193 nm of polymer components suitable for gradedantireflective coating compositions of the disclosure.

DESCRIPTION OF BEST AND VARIOUS MODES FOR CARRYING OUT THE DISCLOSURE

The present disclosure encompasses novel antireflective coatingcompositions which are useful in lithographic processes. In carrying outthe present disclosure, conventional materials and processing techniquescan be employed and, hence, such conventional aspects are not set forthherein in detail. For example, etching of the underlying dielectriclayer is conducted in a conventional manner. One having ordinary skillin the art once aware of the present disclosure could select suitablephotoresist materials and etchants, and employ suitable deposition andetching techniques without undue experimentation.

In the present disclosure, surface energy differences between opticallycontrasting polymer components of a spin-on BARC composition are used asa driving force for the preferential segregation of such componentstowards the ARC-air and ARC-substrate interfaces, so as to create anoptically graded film. This effect can be enhanced in particular caseswhere the optically contrasting polymers have limited mutual miscibilityor are highly immiscible.

The graded BARC prepared in such manner has enhanced antireflectiveproperties compared to a non-graded single layer BARC as discussedherein above. In addition, the present disclosure enables a faster andmore economical processing of the graded BARC, compared to otherstructured BARCs, such as multilayer or graded CVD BARCs, since it canbe coated in one step without the need of using a CVD tool. However, ifdesired additional antireflective coatings could be used in conjunctionwith the graded BARC compositions disclosed herein such as being coatedabove these graded BARC compositions.

The polymers that are employed in the graded BARC formulation areselected in such a way that preferential segregation of one or morecomponents towards the physical interfaces (ARC-air and ARC-substrate)occurs during the film casting and/or film baking process. In polymerblends, differences in interfacial energies, which reflect apreferential interaction, generally cause one polymer to segregate tothe substrate or air interface. For polymer blend constituents havingdifferent hydrophobicity or surface tension, the more hydrophobic orlower surface tension species will typically wet the blend film surfaceduring the coating or baking process. Even slight differences in atomicpolarizability between polymer chains, such as in the case ofhydrogenated polystyrene/deuterated polystyrene (H vs D), can induce asurface energy mismatch and lead to preferential wetting of theblend/air interface (R. A. L. Jones et al. Phys. Rev. Lett. 62, 1989,p.280). Preferential wetting of the blend/substrate interface by one ofthe blend constituents may also occur, based on analog interfacialenergy arguments (D. A. Winesett et al., Polym. Internat. 49, 2000,p.458). Conversely, hydrogen-bonding interactions between polymercomponents can reduce the extent of interfacial segregation (Y. Duan etal., Macromol. 34, 2001, p.6761).

The antireflective coating compositions of the present disclosure arecharacterized by the presence of more than one polymer component. Thosecomponents do not necessarily need to remain thermodynamically miscibleduring the coating and film forming process for the antireflectivecoating to self-assemble into a vertically graded layer. Polymer phaseseparation that occurs perpendicularly to the substrate plane combinedwith preferential substrate wetting by one component can lead tochemically and optically graded films that are absent of detectablesurface defects. Therefore, graded BARC films formed by spin-coatingusing standard processing techniques and tools known to those skilled inthe art render nanoscopically smooth films, suitable for high resolutionlithography patterning.

On the contrary, when lateral phase separation is verified, as in thecase of partially miscible polymers coated on a neutral surface, defectsunder the form of islands, craters, protrusions, roughness, comets,marks, satellite spots, etc. are verified during the simultaneouspolymer demixing and coating process, rendering films with no practicaluse in the field of lithographic patterning for semiconductormanufacturing.

At least one of the polymer components present in the gradedantireflective coating compositions of the present disclosure ischaracterized by having at least one chromophore moiety and at least oneof the polymer components has at least one transparent moiety. Havingthese different moieties imparts the differential optical propertiesrequired for the formation of an optically graded layer. In certainaspects of this disclosure, at least two of the polymer components haveboth at least one chromophore moiety and at least one transparentmoiety. In certain aspects of this disclosure, each of the polymermaterials displays interfacial segregation properties and differentialoptical properties simultaneously. Antireflective coating filmsaccording to this disclosure are optically graded, in a sense that thereal (n) and imaginary (k) part of the complex refractive index varies,which can be substantially continuous, throughout the depth of the filmas a result of the interfacial segregation of the polymer components ofthe film. A typical combination of polymer components with differentialoptical properties is one where the polymer segregating to the bottomsurface of the ARC (substrate-ARC interface) has higher k with respectto the polymer segregating to the top surface of the ARC (ARC-airinterface). Typically the polymer component that exhibits the higherrelative transparency has a k value of about 0 to about 0.5 and the onethat exhibits the higher relative absorbance has a k value of about 0.25to about 1 with the one that exhibits the higher relative absorbancehaving the higher of the k values. When employing two polymers, they aretypically employed in ratios about 10:90 to about 90:10; more typicallyabout 30:70 to about 70:30; even more typically about 60:40 to about40:60, a particular example being about 50:50.

The disclosure also encompasses methods of using the antireflectivecoating compositions disclosed herein to pattern underlying materiallayers on a substrate. The disclosure also encompasses lithographicstructures such as a patterned combination of resist layer andantireflective coating layer.

The antireflective coating compositions of the disclosure generallycomprise:

-   -   a blend of two or more polymer components that chemically differ        from each other, wherein said polymer components are selected        from the group consisting of homopolymers or copolymers selected        from the group consisting of polybisphenols, polysulfones,        polycarbonates, polyhydroquinones, polyphthalates,        polybenzoates, polyphenylethers, polyhydroquinone alkylates,        polycarbamates and polymalonates; and wherein said plurality of        polymer components contain at least one moiety being a        chromophore to preselected imaging radiation wavelength and at        least one moiety transparent to said preselected imaging        radiation wavelength,    -   a crosslinking component, and    -   an acid generator.

The polymer blend typically has solution and film-formingcharacteristics conducive to forming a layer by conventionalspin-coating.

The polymer components that comprise the antireflective coatingcomposition typically contain one or more monomers having one of thefollowing structures shown in FIG. 1, where R1, R1′ can be comprised ofhydrogen, alkyl, cycloalkyl, fluoroalkyl, hydroxyalkyl,hydroxyfluoroalkyl and phenyl entities; R2, R2′ can be selected from agroup consisted of hydrogen, alkyl, fluoroalkyl, carboxyl and hydroxyl;R3, R3′ can be carbonyl-, carboxy-, alkyl-, alkoxy or nitro group; R4 isa hydrogen, hydroxyl, alkoxy, alkyl or phenyl group; R5 is a hydrogen,alkyl or aryl group; and M, M′ are hydroxyalkyl, alkyl, fluoroalkylgroup, benzyl or hydroxybenzl groups. The alkyl groups typically contain1-8 carbon atoms and more typically 1-4 carbon atoms. The cycloalkylgroups typically contain 3-7 carbon atoms.

Functionalization of the above monomers can be performed to selectivelyincorporate the required optical and mechanical properties into thepolymer components, as well as to impart reactivity and solubilityduring formulation and processing of the antireflective coatingcomposition. From a functional standpoint, polymeric structures carryingthe properties mentioned above can be represented by the followingstructure:—[R]_(x)—[R″]_(y)—

-   -   wherein x and y are repeating units.

Wherein R comprises a chromophore or a transparent moiety which alsodefines the limiting etch rate of the polymeric material, while R′comprises a group that is a reactive site for reaction with thecrosslinking component and enhances the interfacial segregationproperties of the polymer with respect to the other polymer componentsof the antireflective film.

The chromophore-containing units or transparent moieties R may containany suitable functional group which (i) can be grafted onto orincorporated into the polymer backbone (ii) has suitable radiationabsorption characteristics, and (iii) does not adversely affect theperformance of the layer or any overlying photoresist layers. For 193 nmradiation, typical chromophore moieties include, but are not limited to,phenyl, naphtalene and anthracene derivatives. Non-aromatic compoundscontaining unsaturated carbon bonds (e.g., carbon-carbon double bonds)are also suitable chromophores.

In the case of 193 nm imaging radiation, the transparent moieties aretypically bulky (C2 or higher) organic moieties substantially free ofunsaturated carbon-carbon bonds. More typical transparent moieties for193 nm applications are adamantane, norbornane, isobornane, camphene,pinane and hexahydroindane derivatives.

R′ comprises a reactive site for reaction with the crosslinkingcomponent. Typical reactive moieties contained in R₂ are alcohols, moretypically aromatic alcohols (e.g., hydroxyphenyl, hydroxymethylphenyl,etc.), aliphatic alcohols (e.g. glyceryl) or cycloaliphatic alcohols(e.g., cyclohexanoyl). Alternatively, non-cyclic alcohols such asfluorocarbon alcohols, aliphatic alcohols, amino groups, vinyl ethers,and epoxides may be used. These aforementioned groups can also impartenhanced solubility in a preferred casting solvent (vide infra) and/ortune the interfacial energy of the polymer by increasing or decreasingthe hydrophobic nature of the polymer with respect to the other polymercomponents of the antireflective film. Contact angle measurements ofwater droplets deposited on the surface of a spin-on film cast from theindividual polymer components of a graded BARC material can be used as acriterion to identify suitable polymers for graded BARC applications andanticipate their interfacial segregation properties. Typically, thepolymer component with the highest contact angle value has a tendency tosegregate to the free surface of the film.

The amount of chromophore units contained in R₁ groups is preferablybalanced with the amount of groups that facilitate cross-linking (R₂) toprovide a desired combination of energy absorption, antireflection andinterfacial segregation. Persons skilled in the art, once aware of thisdisclosure, could select these amounts without undue experimentationdepending upon their desired combination of properties. Eventually,chemical functionalities described for groups R₂ can also carry andimpart the properties required for group R₁, and vice versa. Therefore,alternating copolymers that conform to the properties of R₁ and R₂ canbe used as radiation-absorbing materials that fit the description for agraded BARC given above.

Examples of polymer components suitable for graded BARC applications areshown in FIG. 1, which include:

Poly[4,4′-methylene bisphenol]-co-epichlorohydrin [18-FIG. 1 r],poly[4,4′-ethylidene bisphenol]-co-epichlorohydrin [19-FIG. 1 s],poly[4,4′-isopropylidene bisphenol]-co epichlorohydrin [20-FIG. 1 t],Poly[4,4′-isopropylidenebis(2-methylphenol)]-co-epichlorohydrin [21-FIG.1 u],Poly[4,4′-isopropylidenebis(2,6-dimethylphenol)]-co-epichlorohydrin[22-FIG. 1 v], Poly[4,4′-cyclohexylidene bisphenol]-co-epichlorohydrin[23-FIG. 1 w], Poly[4,4′-(1Phenylethylidene)bisphenol]-co-epichlorohydrin [24-FIG. 1 x],Poly[4,4′(trifluoroisopropylidene) bisphenol]-co-epichlorohydrin[25-FIG. 1 y], Poly[4,4′(hexafluoroisopropylidene)bisphenol]-co-epichlorohydrin [26-FIG. 1 z], Poly[4,4′-sulfonylbisphenol]-co-epichlorohydrin [27-FIG. 1 aa], poly(bisphenol AF adipicester][28-FIG. 1 bb], poly(bisphenol AF succinic ester] [29-FIG. 1 cc],poly[4,4′(hexafluoroisopropylidene)diphthalate-co-epichlorohydrin[30-FIG. 1 dd],poly[4,4′(hexafluoroisopropylidene)diphthalate-co-poly(bisphenol AF)[31-FIG. 1 ee],poly[4,4′(hexafluoroisopropylidene)bis(benzoate)-co-epichlorohydri-n)][32-FIG. 1 ff], poly[3,3′4,4′benzophenonetetracarboxylate-co-epichlorohydrin][33-FIG.1 gg ],poly[4,4′(hexafluoroisopropylidene)diphthalate-co-epichlorohydrin-co-2.6-bis(hydroxymethyl-p-cresol [34-FIG. 1 hh], poly[3,3 ′,4,4′-benzophenonetetracarboxylate-co-epichlorohydrin-co-2.6bis(hydroxyme- thyl-p-cresol][35-FIG. 1ii]poly(terephthalate-co-epichlorohydrin) [36-FIG. 1 jj],poly(2-nitroterephthalate-co-epichlorohydrin) [37-FIG. 1 kk],poly(2-nitrophthalate-co epichlorohydrin) [38-FIG. 1 ll],poly(2-nitroisophthalate-co-epichlorohydrin) [39-FIG. 1 mm],poly(hydroquinone-co-epichlorohydrin) [40-FIG. 1 nn],poly(methylhydroquinone-co epichlorohydrin) [41-FIG. 1 oo],poly(1,2,4-benzenetriol-co-epichlorohydrin) [42-FIG. 1 pp],poly(methylene-bis(41-aminophenyl)-co-glycerol carbamate) [43-FIG. lqq],poly(isopropylidene bis(4-aminophenyl)-co-glycerol carbamate) [44-FIG. 1rr], poly(isopropylidene-bis(3-carboxy-4aminophenyl)-co-glycerolcarbamate) [45-FIG. 1 ss], poly(methylene-bis(4-hydroxyphenyl)-coglycerol carbonate) [46-FIG. 1 tt],poly(isopropylidene-bis(4-hydroxyphenyl)-co-glycerol carbonate) [47 FIG.1 uu], poly(isopropylidene-bis(3-carboxy-4-hydroxyphenyl)-co-glycerolcarbonate) [48-FIG. 1 vv], poly(2-phenyl-1,3-propanediol malonate)[49-FIG. 1 ww], poly(2phenyl-1,3-propanediol 2-methyl-malonate) [50-FIG.lxx], poly(1,3-propanediol benzylidene malonate) [51-FIG. 1 yy],poly(2-phenyl-1,3-propanediol benzylidene-malonate) [52-FIG. 1 zz],poly(bisphenol A-co-epichlorohydrin), glycidyl end-capped [53-FIG. 1aaa].

The polymers of the disclosure typically have a weight average molecularweight, before reaction with the crosslinking component, of at leastabout 1000, more typically up to about 500,000 and even more typically aweight average molecular weight of about 1000-10,000. In certain aspectsof this disclosure, the polymer components typically have a refractiveindex (n) in the range of about 1.3 to about 2.0 and more typically inthe range of about 1.3 to about 1.8, at a pre-selected imaging radiationwavelength. Also, in certain aspects of this disclosure, the polymercomponents typically have an extinction coefficient (k) in the range ofabout 0.001 to about 1.1, at a pre-selected imaging radiationwavelength.

The crosslinking component is typically a crosslinker that can bereacted with all the polymer components present in the antireflectivecoating composition in a manner which is catalyzed by generated acidand/or by heating. Generally, the crosslinking component used in theantireflective coating compositions of the invention may be any suitablecrosslinking agent known in the negative photoresist art which isotherwise compatible with the other selected components of thecomposition. The crosslinking agents typically act to crosslink thepolymer component in the presence of a generated acid. Typicalcrosslinking agents are glycoluril compounds such as tetramethoxymethylglycoluril, methylpropyltetramethoxymethyl glycoluril, andmethylphenyltetramethoxymethyl glycoluril, available under thePOWDERLINK trademark from Cytec Industries. Other possible crosslinkingagents include: 2,6-bis(hydroxymethyl)-p-cresol compounds such as thosedisclosed in Japanese Laid-Open Patent Application (Kokai) No. 1-293339,etherified amino resins, for example methylated or butylated melamineresins (N-methoxymethyl- or N-butoxymethyl-melamine respectively), andmethylated/butylated glycolurils, for example as disclosed in CanadianPatent No. 1 204 547. Other crosslinking agents such as bis-epoxies orbis-phenols (e.g., bisphenol-A) may also be used. Combinations ofcrosslinking agents may be used.

The acid generator is typically a thermal acid generator compound thatliberates acid upon thermal treatment. A variety of known thermal acidgenerators are suitably employed such as e.g.2,4,4,6-tetrabromocyclohexadienone, benzoin tosylate, 2-nitrophenyltosylate and other alkyl esters of organic sulfonic acids. Compoundsthat generate a sulfonic acid upon activation are generally suitable.Other suitable thermally activated acid generators are described in U.S.Pat. Nos. 5,886,102 and 5,939,236. If desired, a radiation-sensitiveacid generator may be employed as an alternative to a thermallyactivated acid generator or in combination with a thermally activatedacid generator. Examples of suitable radiation-sensitive acid generatorsare described in U.S. Pat. Nos. 5,886,102 and 5,939,236. Otherradiation-sensitive acid generators known in the resist art may also beused as long as they are compatible with the other components of theantireflective composition. Where a radiation-sensitive acid generatoris used, the cure (crosslinking) temperature of the composition may bereduced by application of appropriate radiation to induce acidgeneration which in turn catalyzes the crosslinking reaction. Even if aradiation-sensitive acid generator is used, it is preferred to thermallytreat the composition to accelerate the crosslinking process (e.g., forwafers in a production line). Mixtures of acid generators may be used.

The antireflective coating compositions of the present disclosure willtypically contain a solvent prior to their application to the desiredsubstrate. The solvent may be any solvent conventionally used withresists which otherwise does not have any excessively adverse impact onthe performance of the antireflective composition. Typical solvents arepropylene glycol monomethyl ether acetate, cyclohexanone, and ethyllactate. The amount of solvent in the composition for application to asubstrate is typically sufficient to achieve a solids content of about2-20 wt. %. Higher solids content formulations will generally yieldthicker coating layers. The compositions of the present disclosure mayfurther contain minor amounts of auxiliary components (e.g., baseadditives, etc.) as may be known in the art.

The antireflective coating compositions of the present disclosure can beprepared by combining the polymer, crosslinking component and acidgenerator, and any other desired ingredients using conventional methods.The compositions of the present disclosure advantageously may be formedinto antireflective coating layers on a substrate by spin-coatingfollowed by baking to achieve crosslinking and solvent removal. Thebaking is typically conducted at about 250° C. or less, more preferablyabout 150° C.-220° C. The baking time may be varied depending on thelayer thickness and bake temperature.

The thickness of the antireflective coating composition of the presentdisclosure may be varied depending on the desired function. For typicalapplications, the thickness of the composition is typically about100-10000 Å, more typically about 200-2000 Å. The compositions of theinvention can have etch resistant properties that are lower, equal orhigher than those photoresist materials that are conventionally used in193 nm photolithography and whose etch properties are known to thoseskilled in the art.

The antireflective coating compositions of the present disclosure areespecially useful for lithographic processes used in the manufacture ofintegrated circuits on semiconductor substrates. The compositions areespecially useful for lithographic processes using deep-UV radiationsuch as 193 nm light.

Semiconductor lithographic applications generally involve transfer of apattern to a layer of material on the semiconductor substrate. Thematerial layer of the semiconductor substrate may be a metal conductorlayer, a ceramic insulator layer, a semiconductor layer or othermaterial depending on the stage of the manufacture process and thedesired material set for the end product. The composition of the presentdisclosure is typically applied directly over the material layer to bepatterned, typically by spin-coating. The composition is then baked toremove solvent and cure (crosslink) the composition. Aradiation-sensitive resist layer can then be applied (directly orindirectly) over the cured antireflective composition.

Typically, the solvent-containing resist composition is applied usingspin coating or other technique. The substrate with the resist coatingis then typically heated (pre-exposure baked) to remove the solvent andimprove the coherence of the resist layer. The thickness of the appliedlayer is typically as thin as possible with the provisos that thethickness is typically substantially uniform and that the resist layerbe sufficient to withstand subsequent processing (typically reactive ionetching) to transfer the lithographic pattern to the underlyingsubstrate material layer. The pre-exposure bake step is preferablyconducted for about 10 seconds to 15 minutes, more preferably about 15seconds to 2 minutes. The pre-exposure bake temperature may varydepending on the glass transition temperature of the photoresist.

After solvent removal, the resist layer is then patternwise-exposed tothe desired radiation (e.g. 193 nm ultraviolet radiation). Typically,with wave-like radiation such as 193 nm ultraviolet radiation, thepatternwise exposure is conducted through a mask which is placed overthe resist layer. For 193 nm UV radiation, the total exposure energy istypically about 100 mJ/cm² or less, more typically about 50 mJ/cm² orless (e.g. 15-30 mJ/cm²).

After the desired patternwise exposure, the resist layer is typicallybaked to further complete the acid-catalyzed reaction and to enhance thecontrast of the exposed pattern. The post-exposure bake is typicallyconducted at about 60° C.-175° C., more preferably about 90° C.-160° C.The post-exposure bake is typically conducted for about 30 seconds to 5minutes.

After post-exposure bake, the resist structure with the desired patternis obtained (developed) by contacting the resist layer with an alkalinesolution which selectively dissolves the areas of the resist which wereexposed to radiation. Typical alkaline solutions (developers) areaqueous solutions of tetramethyl ammonium hydroxide. The resultinglithographic structure on the substrate is then typically dried toremove any remaining developer solvent.

The pattern from the resist structure may then be transferred to theexposed portions of the layer of antireflective material of the presentdisclosure by etching with CF₄ or other suitable etchant usingtechniques known in the art.

After the opening of the layer of antireflective coating layer of thepresent disclosure, the underlying material layer to be patterned maythen be etched using an etchant appropriate to the material layercomposition. Where the material layer is a metal (e.g., Cr) acombination of Cl₂/O₂ may be used as a dry etchant.

Once the desired pattern transfer has taken place, any remaining resistmay be removed using conventional stripping techniques.

Thus, the compositions of the present disclosure and resultinglithographic structures can be used to create patterned material layerstructures such as metal wiring lines, holes for contacts or vias,insulation sections (e.g., damascene trenches or shallow trenchisolation), trenches for capacitor structures, etc. as might be used inthe design of integrated circuit devices. The compositions areespecially useful in the context of creating patterned layers of oxides,nitrides or polysilicon.

Examples of general lithographic processes where the composition of thepresent disclosure may be useful are disclosed in U.S. Pat. Nos.4,855,017; 5,362,663; 5,429,710; 5,562,801; 5,618,751; 5,744,376;5,801,094; 5,821,469 and 5,948,570. Other examples of pattern transferprocesses are described in Chapters 12 and 13 of “SemiconductorLithography, Principles, Practices, and Materials” by Wayne Moreau,Plenum Press, (1988). It should be understood that the invention is notlimited to any specific lithographic technique or device structure.

The present disclosure is particularly effective in reducing themonochromatic radiation reflected from buried interfaces into thephotoresist imaging layer to intensity levels that do not cause anydetrimental effect on the accuracy with which photoresist structures aredefined. In the case where the semiconductor substrate comprises asubstantially transparent substrate containing various topographicalfeatures, such as topographical features at different depths within thesubstrate, the present disclosure tends to ameliorate the reflectivenotching problem.

Compositions of the present disclosure are capable of providingoutstanding optical, mechanical and etch selectivity properties whilebeing applicable for use in spin-on application techniques as discussedabove.

The following non-limiting examples are provided to further illustratethe present invention. Because the examples are provided forillustrative purposes only, the invention embodied therein should not belimited thereto.

EXAMPLES Example 1

Materials Synthesis (Polymer 43)—A round bottom flask was charged withpyridine (5 mL) and glycerol (5.1 mmol, 470 mg).4,4′-Methylene-bis(phenyl isocyanate) (5 mmol, 1.25 g) was added and thereaction mixture was stirred for 20 hours at ambient temperature. Thenit was poured into 100 mL of 1 M HCl, the solids were filtered off andvacuum dried. The material was further purified by dissolving in DMF andpouring into vigorously stirred water. After filtration and vacuumdrying, 800 mg of polymer 43 (FIG. 1 qq) was obtained.

Example 2

Optical and Physical Properties—The optical constants (the index ofrefraction n and the extinction coefficient k) of individual componentssuitable for graded BARC applications are measured at a radiationwavelength of 193 nm using a Variable Angle Spectroscopic Ellipsometer(VASE) manufactured by J. A. Woollam, Inc. The optical properties ofindividual polymer components are shown in FIG. 3.

Example 3

Formulation—Polymer components are dissolved in propylene glycolmonomethyl ether acetate (PGMEA) in individual concentrations of 50parts by weight each (1.8% by weight each with respect to the solvent).One polymer component has an extinction coefficient k higher than 0.5.Another polymer component has an extinction coefficient k lower than0.5. A crosslinking agent tetramethoxymethyl glycoluril, available fromDayChem, in a concentration of 10 parts by weight anddi(t-butylphenyl)iodonium perfluorobutylsulfonate (DtBPI—PFBuS) in aconcentration of 5 parts by weight are added to the solution, achieving4.2 wt. % by weight of total solids.

Example 4

Film Formation—Formulations, prepared as described in Example 3, arespin coated onto a 300 mm silicon wafer at 1500 rpm for 60 sec. The filmthickness is about 750 Å. The spin cast film is cured in two steps. Thefirst bake step is carried at 130° C. for 60 sec, after which the wafersare allowed to cool down to room temperature on a chill plate. Thesecond bake step is carried at 220° C. for 120 sec., after which thewafers are allowed to cool down to room temperature on a chill plateagain.

The term “comprising” (and its grammatical variations) as used herein isused in the inclusive sense of “having” or “including” and not in theexclusive sense of “consisting only of”. The terms “a” and “the” as usedherein are understood to encompass the plural as well as the singular.

The foregoing description illustrates and describes the presentdisclosure. Additionally, the disclosure shows and describes only thepreferred embodiments of the disclosure, but, as mentioned above, it isto be understood that it is capable of changes or modifications withinthe scope of the concept as expressed herein, commensurate with theabove teachings and/or skill or knowledge of the relevant art. Theembodiments described hereinabove are further intended to explain bestmodes known of practicing the invention and to enable others skilled inthe art to utilize the disclosure in such, or other, embodiments andwith the various modifications required by the particular applicationsor uses disclosed herein. Accordingly, the description is not intendedto limit the invention to the form disclosed herein. Also, it isintended that the appended claims be construed to include alternativeembodiments.

All publications, patents and patent applications cited in thisspecification are herein incorporated by reference, and for any and allpurposes, as if each individual publication, patent or patentapplication were specifically and individually indicates to beincorporated by reference. In the case of inconsistencies, the presentdisclosure will prevail.

We claim:
 1. A method of forming a patterned material layer on asubstrate, the method comprising: (a) providing a substrate having asurface; (b) depositing an antireflective coating layer comprising anantireflective coating composition on the substrate surface by spincoating, upon which an uniaxial optical gradient is formed within saidantireflective coating layer in a direction orthogonal to the substratesurface; (c) depositing a photoresist composition on the antireflectivecoating layer to form a photoresist layer; (d) optionally applying atopcoat layer; (e) pattern-wise exposing the coated substrate to animaging radiation; (f) contacting the coated substrate with a developerfor removing a portion of the photoresist layer, and, if present, forremoving the topcoat layer, to thereby form a patterned photoresistlayer wherein the antireflective coating composition comprises: (a) aplurality of polymer components that chemically differ from each other,wherein at least one polymer component is selected from the groupconsisting of a polybisphenol, a polysulfone, a polycarbonate, apolyhydroquinone, a polyphthalate, a polybenzoate, a polyphenylether, apolyhydroquinone alkylate, a polycarbamate and a polymalonate andmixtures thereof and wherein said plurality of polymer componentscontain at least one moiety being a chromophore to a preselected imagingradiation wavelength and at least one moiety transparent to thepreselected imaging radiation wavelength, (b) a separate crosslinkingcomponent, and (c) an acid generator, wherein the plurality of polymercomponents comprises two components which substantially segregatebetween a first interface, the first interface being between theantireflective coating layer and the substrate, and a second interface,the second interface being between the antireflective coating layer andthe photoresist layer; wherein said polymer components are randomcopolymers; and wherein said polymer components comprise a plurality ofreactive sites distributed along said polymer for reaction with saidcrosslinking component.
 2. The method of claim 1, wherein said acidgenerator is a thermally activated acid generator.
 3. The method ofclaim 1, wherein said crosslinking component comprises a glycolurilcompound.
 4. The method of claim 1, wherein the plurality of polymercomponents have a refractive index (n) in the range of about 1.3 toabout 2.0 at the preselected imaging radiation wavelength.
 5. The methodof claim 1, wherein the plurality of polymer components have anextinction coefficient (k) in the range of about 0.001 to about 1.1, atthe preselected imaging radiation wavelength.
 6. The method of claim 1,wherein at least one polymer component is highly absorbing at thepreselected imaging radiation wavelength.
 7. The method of claim 1,wherein the plurality of polymer components have a tunable molecularweight ranging from about 1000 to about 500,000.
 8. The method of claim1, wherein said acid generator is a thermally activated acid generator,wherein said crosslinking component comprises a glycoluril compound,wherein the polymer components have a refractive index (n) in the rangeof about 1.3 to about 2.0, at the imaging radiation wavelength, whereinthe polymer components have an extinction coefficient (k) in the rangeof about 0.001 to about 1.1, at the imaging radiation wavelength,wherein at least one polymer component is highly absorbing at theimaging radiation wavelength and wherein the polymer components have atunable molecular weight ranging from about 1,000 to about 500,000. 9.The method of claim 1, wherein forming the antireflective coating andphotoresist layers includes approximately matching the index ofrefraction (n) of the antireflective coating and photoresist layers atthe interface between both said layers; wherein the extinctioncoefficient (k) of the uniaxially graded antireflective coatingcontinuously increases in a direction away from the interface betweenthe antireflective coating and photoresist layers; wherein theantireflective coating layer has a uniform thickness of about 200 toabout 2000 Angstroms on the substrate; wherein the substrate is selectedfrom the group consisting of ceramic, dielectric, metal andsemiconductor layer; wherein the pattern in the photoresist layer istransferred to the substrate by removing portions of the substrate notcovered by the patterned photoresist layer; wherein portions ofsubstrate are removed by etching the material layer in areas not coveredby the patterned photoresist layer; and wherein portions of thesubstrate are removed by using reactive ion etching.
 10. A method forforming a patterned material layer comprising: spin-coating a pluralityof polymer components that chemically differ from each other, acrosslinking component, and an acid generator onto a substrate to form asingle-layer graded antireflective coating, wherein the plurality ofpolymer components contain at least one moiety being a chromophore to apreselected imaging radiation wavelength and at least one moietytransparent to the preselected imaging radiation wavelength, disposing aphotoresist layer on the single-layer graded antireflective coating;there being a first interface between the single-layer gradedantireflective coating and the photoresist; there being a secondinterface between the single-layer graded antireflective coating and thesubstrate; wherein the plurality of polymer components comprises twocomponents which substantially segregate between the first interface andthe second interface; patterning the single-layer composite gradedantireflective coating and the photoresist; wherein the plurality ofpolymer components are random copolymers comprising moieties selectedfrom the group consisting of polybisphenols, polysulfones,polycarbonates, polyhydroquinones, polyphthalates, polybenzoates,polyphenylethers, polyhydroquinone alkylates, polycarbamates andpolymalonates; and wherein the plurality of polymer components comprisea plurality of reactive sites distributed along the plurality of polymercomponents for reaction with the crosslinking component.
 11. A methodfor forming a patterned material layer on a substrate comprising:providing a substrate having a material layer on a surface thereof;forming a single-layer graded antireflective coating layer over thematerial layerby spin- coating a single-layer graded antireflectivecoating composition comprising a plurality of polymer components thatchemically differ from each other and wherein said plurality of polymercomponents contain at least one moiety being a chromophore topreselected imaging radiation wavelength and at least one moietytransparent to said preselected imaging radiation wavelength; depositinga photoresist composition on the single-layer graded antireflectivecoating layer to form a photoresist imaging layer on the material;optionally applying a topcoat layer; patternwise exposing thephotoresist imaging layer to radiation thereby creating a pattern ofradiation-exposed regions in the photoresist imaging layer, selectivelyremoving portions of the photoresist imaging layer to expose portions ofthe material layer, and etching the exposed portions of the materiallayer, thereby forming the patterned material feature wherein saidplurality of polymer components comprises two components whichsubstantially segregate between a first interface and a secondinterface; said single-layer composite graded antireflection coatingcomposition further comprises a crosslinking component and an acidgenerator, wherein said polymer components are random copolymerscomprising moieties selected from the group consisting ofpolybisphenols, polysulfones, polycarbonates, polyhydroquinones,polyphthalates, polybenzoates, polyphenylethers, polyhydroquinonealkylates, polycarbamates and polymalonates , and wherein said polymercomponents comprise a plurality of reactive sites distributed along saidpolymer for reaction with said crosslinking component.
 12. A structurecomprising: a single-layer graded antireflective coating on a substrate,wherein the single-layer graded antireflective coating comprises acrosslinker, an acid generator, and a plurality of polymer componentsthat chemically differ from each other and wherein the plurality ofpolymer components contain at least one moiety being a chromophore to apreselected imaging radiation wavelength and at least one moietytransparent to the preselected imaging radiation wavelength locatedbeneath a photoresist layer; the photoresist layer being disposed on thesingle-layer graded antireflective coating; there being a firstinterface between the single-layer graded antireflective coating and thephotoresist layer; there being a second interface between thesingle-layer composite graded antireflective coating and the substrate;the plurality of polymer components within the single-layer compositegraded antireflective coating substantially segregate between the firstinterface and the second interface; further comprising a pattern in saidsingle-layer graded antireflective coating and said photoresist layer;said polymer components are random copolymers comprising moietiesselected from the group consisting of a polybisphenols, polysulfones,polycarbonates, polyhydroquinones, polyphthalates, polybenzoates,polyphenylethers, polyhydroquinone alkylates, polycarbamates andpolymalonates; wherein said polymer components comprise a plurality ofreactive sites distributed along said polymer for reaction with saidcrosslinking component.